"The performance of the two cameras is similar, but from ISO 6400 upwards the Nikon D4 is the winner by a little margin: I'd say that it has about 0.5 stop better high ISO performance than the 1DX; the D4 shows a little more noise and it has a more easy to remove, fine granulated noise."

Glad I own a 1D X. But then again the noise and color accuracy are fixable. You can't fix the price difference. Still, I must say the settings are kind of ridiculous. 1/6400 at F2.2? My best friend has a 5D III. I will try to do a comparison too to see how they perform with the new 24-70 II

Since it doesn't seem to be possible to post on the website of the tester I'd like to post here:

Due to the fact that the 5D3 pictures are brighter than the 1DX it appears to me that Canon used a little trick to "improve" the 1DX's noise performance, which is that the Camera displays ISO 25,600 but in fact it uses just ISO 20,000 or so. If both cameras were using the same ISO-speed the brightness should match in my opinion. Of course the 1DX is supposed to have better noise performance at ISO 20,000 than the 5D3 on 25,600.

So i think that a second comparison should be done using exactly the same brightness (which means the same ACTUALLY ISO-speed) while disregarding displayed ISO numbers. This should show the real difference in noise between the two cameras.

The metering difference I don't get why people are using as an argument when it comes to iso evaluation. First off, which metering is more accurate? Absolutely no contest ... and in the X you can offset your 0 ev, mine is at +5/8. I've shot 20k shots on the 5d3 and 11k on the 1d X and the difference is huge in metering precision and noiseperformance. I always need to to adjust the metering back and forth on the 5d to get what I want which really slows down shooting, is very annoying and makes me miss moments. The 1d is consistent no matter what light it's crazy, i hardly ever touch the ev scale. I guess all the 5d owners don't know or don't want to know and needs to defend their purchase. I too defend the 1d X over the 5d, and i have used them both to the limits. And it just isn't right the difference is minor and not worth the price. It might not be worth it to some people, but the 1d is twice the camera.

As a professional who has shot cars and trucks for car makers and their agencies for over 25 years, let me say that it is highly unlikely that there would be much if any difference in the color rendition of the two cameras had the color of the lighting been identical. As others have already pointed out, the color of the cloud bank reflected in the windshield of the 5D3 is obviously hugely warmer than the clouds reflected in the windshield of the 1DX. There is no question in my mind that this accounts for the vast majority, if not 100%, of the color difference.

At sunset, when clouds across the horizon are moving quickly, dissapating due to weather front movement or, more likely, atmospheric cooling that reduces the amount of evaporated water vapor in the air, the sky color often changes very rapidly as the very warm (low color temperatrure expressed in Kelvin degrees) source of light from the low-sky direct sunlight may be revealed as it peeks out between low hanging cumulus clouds, or is revealed as the clouds covering it are thinned out or disappear entirely. If you look at the reflection in the 5D3 windshield, one can see this effect in the reflected clouds which have obviously been lit by much warmer light from the setting sun. This is all very clear from the examples.

As to the color noise, it was also very much affected by the color temperature. The "grain" size and frequency of the noise was obviously affected by the warmer color light; because the subject was much warmer (redder) in the 5D3 shot, it was recorded much more heavily in the red channel, the channel which always reproduces much more noise than either the blue or green channels. This is the same reason why images lit by low light tungsten lighting are always noisier than those lit by low light daylight-colored light sources. You can easily see this by the vastly greater number of red noise clumps in the 5D3 shot, making the image look more "noisy" than the image from the cooler (less red, more blue and green) lit 1DX shot.

To summarize, the color rendition issue is probably due entirely to ambient color temperatures at the time of each shot, and the noise differences are probably almost as much due to the same influence; without the color change, the 1DX probably would still have had less noise, but only a tiny fraction less, and the noise evident on the 5D3 would have been of the same general color range as visible in the shot taken with the 1DX.

As a professional who has shot cars and trucks for car makers and their agencies for over 25 years, let me say that it is highly unlikely that there would be much if any difference in the color rendition of the two cameras had the color of the lighting been identical. As others have already pointed out, the color of the cloud bank reflected in the windshield of the 5D3 is obviously hugely warmer than the clouds reflected in the windshield of the 1DX. There is no question in my mind that this accounts for the vast majority, if not 100%, of the color difference.

At sunset, when clouds across the horizon are moving quickly, dissapating due to weather front movement or, more likely, atmospheric cooling that reduces the amount of evaporated water vapor in the air, the sky color often changes very rapidly as the very warm (low color temperatrure expressed in Kelvin degrees) source of light from the low-sky direct sunlight may be revealed as it peeks out between low hanging cumulus clouds, or is revealed as the clouds covering it are thinned out or disappear entirely. If you look at the reflection in the 5D3 windshield, one can see this effect in the reflected clouds which have obviously been lit by much warmer light from the setting sun. This is all very clear from the examples.

As to the color noise, it was also very much affected by the color temperature. The "grain" size and frequency of the noise was obviously affected by the warmer color light; because the subject was much warmer (redder) in the 5D3 shot, it was recorded much more heavily in the red channel, the channel which always reproduces much more noise than either the blue or green channels. This is the same reason why images lit by low light tungsten lighting are always noisier than those lit by low light daylight-colored light sources. You can easily see this by the vastly greater number of red noise clumps in the 5D3 shot, making the image look more "noisy" than the image from the cooler (less red, more blue and green) lit 1DX shot.

To summarize, the color rendition issue is probably due entirely to ambient color temperatures at the time of each shot, and the noise differences are probably almost as much due to the same influence; without the color change, the 1DX probably would still have had less noise, but only a tiny fraction less, and the noise evident on the 5D3 would have been of the same general color range as visible in the shot taken with the 1DX.

Ummm... wasn't this already known from the start. From the initial batch of high ISO 5D3 pictures I've seen, there was always a color shift when going from 12800 to 25600. If the photo was taken with the 5D3 at 12800 then there wouldn't be a color shift. In either case, the color shift can be corrected in post and is the least of your worries.

The metering difference I don't get why people are using as an argument when it comes to iso evaluation. First off, which metering is more accurate? Absolutely no contest ... and in the X you can offset your 0 ev, mine is at +5/8. I've shot 20k shots on the 5d3 and 11k on the 1d X and the difference is huge in metering precision and noiseperformance. I always need to to adjust the metering back and forth on the 5d to get what I want which really slows down shooting, is very annoying and makes me miss moments. The 1d is consistent no matter what light it's crazy, i hardly ever touch the ev scale. I guess all the 5d owners don't know or don't want to know and needs to defend their purchase. I too defend the 1d X over the 5d, and i have used them both to the limits. And it just isn't right the difference is minor and not worth the price. It might not be worth it to some people, but the 1d is twice the camera.

I have both and use both heavily. There's not a bit damn difference that makes any difference in metering between the two cameras. We're talking 1/3 of a stop. It doesn't cost me any photos and noise cleanup at ISO 12,800 is similar, they're both highly useable and I've printed 8 x 10's from BOTH at that ISO level and they look great. I suppose I'm just defending my purchase of the 5D3 and justifying it? Well yeah, with facts and everyday useage. It seems to me you're doing the same thing with the 1DX that you accuse 5D3 owners of doing, aren't you? No offense meant, however. It just seems you're doing the exact same thing about the 1DX as supposedly 5D3 owners are doing.

"The performance of the two cameras is similar, but from ISO 6400 upwards the Nikon D4 is the winner by a little margin: I'd say that it has about 0.5 stop better high ISO performance than the 1DX; the D4 shows a little more noise and it has a more easy to remove, fine granulated noise."

He still doesn't understand the difference between noise per pixel and noise per image. He's also not saying how he got the same image resolution and field of view for different sensor resolutions. Were the cameras at different distances? Did he resize the images?

Nevertheless, I appreciate his effort in getting the gear and making the images. The 1DX's noise is blotchier.

The metering difference I don't get why people are using as an argument when it comes to iso evaluation.

Because the amount of light that gets on the sensor affects the noise level. The ISO doesn't change the amount of light that gets on the sensor. Therefore, identical optical exposures are mandatory. For a scientific test, the ISO has to be changed so that the brightness of the images from both sensors is the same, which means that the displayed ISO value may be different.

The metering difference I don't get why people are using as an argument when it comes to iso evaluation.

Because the amount of light that gets on the sensor affects the noise level. The ISO doesn't change the amount of light that gets on the sensor. Therefore, identical optical exposures are mandatory. For a scientific test, the ISO has to be changed so that the brightness of the images from both sensors is the same, which means that the displayed ISO value may be different.

Yeah, for a scientific test point. But when metering and shooting a scene it doesn't matter. Less light more noise, but if one camera always meter under it creates noise. And when things happen fast and the metering is off, like with all three 5d's, that underexposes the problem isn't the displayed iso's. The difference is lab tests and how the camera creates the picture.